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    <meta charset="UTF-8">
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    <title>Document</title>
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<body>
    
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<script>
    let arr = [
        {day:1},
        {day:2},
        {day:3},
    ]
    let list = []
     arr.map(e => list.push(e.day))
    console.log(list)
</script>
</html>